[Rh(7-SPh-8-Me-7,8-C_2B_9H_(10))(PPh_3)_2]: A New Rhodacarborane with Enhanced Activity in the Hydrogenation of 1-Alkenes

摘要

The use of rhodacarboranes as homogeneous catalysis lor the hydrogenation and isomerization of alkenes was first reported by Hawthorne and co-workers, and their utility was later extended to other catalytic transformations. A thorouuh mechanistic study attributed the catalytic activity to the formation of B Rh~(III)-H species by the oxidative addition of terminal B-H bonds to Rh~I centers in exi-nido-rhodacarborane derivatives. Besides, the formation of nonactive closo-rhodacarborane tautomers and the involvement in the catalytic cycle of B-H-Rh~I species attached to the less active "lower bell" of the carborane framew ork were two reasons proposed to account for the lower activity of some of the catalysts tested (Fig. 1).